1. Field of the Invention
The present invention relates to a semiconductor device, a liquid crystal display device, and the like. Note that in this specification, a semiconductor device refers to a semiconductor element itself or a device including a semiconductor element. As an example of such a semiconductor element, for example, a transistor (a thin film transistor or the like) can be given. In addition, a semiconductor device also refers to a display device such as a liquid crystal display device.
2. Description of the Related Art
A conventional liquid crystal display device has a structure in which a liquid crystal layer including a liquid crystal material is sandwiched between a substrate including a thin film transistor (also referred to as a thin film transistor (TFT) substrate) and a counter substrate. The TFT substrate has a layered structure in which a glass substrate, a base insulating film, a gate electrode, a gate insulating film, a semiconductor layer, source and drain electrodes, an interlayer insulating film, a pixel electrode, and an alignment film are stacked in this order. The counter substrate has a layered structure in which a glass substrate, a black matrix layer (an organic resin or metal), a color filter, a counter electrode, and an alignment film are stacked in this order.
In order to prevent a thin film transistor provided in a pixel portion on the TFT substrate from being irradiated with light from a backlight or light from the outside, in the liquid crystal display device, the black matrix layer is provided in a region of the counter substrate which overlaps with the thin film transistor.
In addition, in order to improve image quality, in the conventional liquid crystal display device, a black matrix layer is also provided in a region of the counter substrate, which is over a region of the TFT substrate where projections and depressions due to a variety of metal wirings, a holding capacitor, or the like exist.
However, in the case where the black matrix layer is provided on the counter substrate, there is a problem in that light leakage occurs due to misregistration between the counter substrate and the TFT substrate, so that the thin film transistor of the TFT substrate is irradiated with the light.
In addition, when the width of the black matrix layer is extended to a designed value or more in the counter substrate in order to prevent light leakage even if misregistration between the counter substrate and the TFT substrate occurs, the aperture ratio of the pixel portion might be reduced.
In recent years, higher resolution of a liquid crystal display device has been advanced as well as higher-speed driving thereof. Therefore, a display panel having a large number of pixels and displaying a high-resolution image has problems in that adverse effects caused by a load of parasitic capacitance between wirings, a load due to an increase in the number of signal lines, or the like are increased.